People are like bicycles. ...

People are like bicycles. They can keep their balance only as long as they keep moving.
People are like bicycles. They can keep their balance only as long as they keep moving.

Quotes from the same author

It is characteristic of the military mentality that non-human factors ... are held essential, while the human being, his desires and thoughts-in short, the psychological factors-are considered as unimportant and secondary.
In the middle of every difficulty lies opportunity.
You can't blame gravity for falling in love.
One may say the eternal mystery of the world is its comprehensibility.
The human spirit must prevail over technology.